1,5-Cyclooctadiene

1,5-Cyclooctadiene
Systematic name Cycloocta-1,5-diene[1]
Identifiers
Abbreviations	1,5-COD
CAS number	111-78-4 Y, 1552-12-1 (1Z,5Z)-1,5-diene, 5259-71-2 (1Z,5E)-1,5-diene, 17612-50-9 (1E,5E)-1,5-diene
PubChem	8135, 10937607 (5Z)-5-ene, 82916 (1Z,5Z)-1,5-diene, 5364364 (1Z,5E)-1,5-diene, 5702534 (1E,5E)-1,5-diene
ChemSpider	7843 N, 74815 (1Z,5Z)-1,5-diene Y, 18520443 (1Z,5E)-1,5-diene Y, 19971660 (1E,5E)-1,5-diene Y
EC number	203-907-1
UN number	2520
MeSH	1,5-cyclooctadiene
RTECS number	GX9560000 GX9620000 (1Z,5Z)-1,5-diene
Beilstein Reference	2036542 1209288 (1Z,5Z)-1,5-diene
Jmol-3D images	Image 1
SMILES C1CC=CCCC=C1
InChI InChI=1S/C8H12/c1-2-4-6-8-7-5-3-1/h1-2,7-8H,3-6H2/b2-1-,8-7- Y Key: VYXHVRARDIDEHS-QGTKBVGQSA-N Y InChI=1/C8H12/c1-2-4-6-8-7-5-3-1/h1-2,7-8H,3-6H2/b2-1-,8-7- Key: VYXHVRARDIDEHS-QGTKBVGQBM
Properties
Molecular formula	C8H12
Molar mass	108.18 g mol−1
Exact mass	108.093900384 g mol-1
Appearance	Colorless liquid
Density	882 mg cm-3
Melting point	-69 °C, 204 K, -92 °F
Boiling point	150 °C, 423 K, 302 °F
Vapor pressure	910 Pa
Refractive index (nD)	1.493
Thermochemistry
Std enthalpy of formation ΔfHo298	21-27 kJ mol-1
Std enthalpy of combustion ΔcHo298	-4.890--4.884 MJ mol-1
Standard molar entropy So298	250.0 J K-1 mol-1
Specific heat capacity, C	198.9 J K-1 mol-1
Hazards
GHS pictograms
GHS signal word	DANGER
GHS hazard statements	H226, H304, H315, H317, H319, H334
GHS precautionary statements	P261, P280, P301+310, P305+351+338, P331, P342+311
EU classification	Xn
R-phrases	R10, R36/38, R42/43, R65
S-phrases	S23, S26, S36/37, S62
Flash point	32-38 °C
Autoignition temperature	222 °C
N (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

1,5-Cyclooctadiene is the organic compound with the chemical formula C₈H₁₂. Generally abbreviated COD, this diene is a useful precursor to other organic compounds and serves as a ligand in organometallic chemistry.^[2][3]

Synthesis

1,5-Cyclooctadiene can be prepared by dimerization of butadiene in the presence of a nickel catalyst, a coproduct being vinylcyclohexene. Approximately 10,000 tons were produced in 2005.^[4]

Organic reactions

COD reacts with borane to give 9-borabicyclo[3.3.1]nonane,^[5] commonly known as 9-BBN, a reagent in organic chemistry used in hydroborations:

COD adds SCl₂ (or similar reagents) to give 2,6-dichloro-9-thiabicyclo[3.3.1]nonane:^[6]

The resulting dichloride can be further modified as the di-azide or di-cyano derivative in a nucleophilic substitution aided by anchimeric assistance.

Metal complexes

1,5-COD typically binds to low-valence metals via both alkene groups. The complex Ni(cod)₂ is a precursor to several nickel(0) and Ni(II) complexes. Metal-COD complexes are attractive because they are sufficiently stable to be isolated, often being more robust than related ethylene complexes. The stability of COD complexes is attributable to the chelate effect. The COD ligands are easily displaced by other ligands, such as phosphines.

Structure of M(cod)₂ for M = Ni, Pd, Pt.

Ni(COD)₂ is prepared by reduction of anhydrous nickel acetylacetonate in the presence of the ligand, using triethylaluminium ^[7]

1/3 [Ni(C₅H₇O₂)₂]₃ + 2 COD + 2 Al(C₂H₅)₃ → Ni(COD)₂ + 2 Al(C₂H₅)₂(C₅H₇O₂) + C₂H₄ + C₂H₆

The related Pt(COD)₂ is prepared by a more circuitous route involving the dilithium cyclooctatetraene:^[8]

Li₂C₈H₈ + PtCl₂(COD) + 3 C₇H₁₀ → [Pt(C₇H₁₀)₃] + 2 LiCl + C₈H₈ + C₈H₁₂

Pt(C₇H₁₀)₃ + 2 COD → Pt(COD)₂ + 3 C₇H₁₀

Extensive work has been reported on complexes of COD, much of which can has been described in volumes 25, 26, and 28 of Inorganic Syntheses. The platinum complex has been used in many syntheses:

Pt(COD)₂ + 3 C₂H₄ → Pt(C₂H₄)₃ + 2 COD

COD complexes are useful as starting materials, one noteworthy example is the reaction:

Ni(cod)₂ + 4 CO_(g) $\rightleftharpoons$ Ni(CO)₄ + 2 COD

The product Ni(CO)₄ is highly toxic, thus it is advantageous to generate it in the reaction vessel as opposed to being dispensed directly. Other low-valent metal complexes of COD include Mo(COD)(CO)₄, [RuCl₂(COD)]_n, and Fe(COD)(CO)₃. COD is an especially important in the coordination chemistry of rhodium(I) and iridium(I), examples being Crabtree's catalyst and cyclooctadiene rhodium chloride dimer. The square planar complexes [M(COD)₂]⁺ are known (M = Rh, Ir).

(E,E)-COD

E,E-COD synthesis (Stöckmann et al. 2011)

The highly strained trans-trans isomer of 1,5-cyclooctadiene is a known compound. (E,E)-COD was first synthesized by Whitesides and Cope in 1969 by photoisomerization of the cis compound.^[9] Another synthesis (double elimination reaction from a cyclooctane ring) was reported by Huisgen in 1987.^[10] The molecular conformation of (E,E)-COD is twisted rather than chair-like. The compound has been investigated as a click chemistry mediator.^[11]

References

1. ^ "AC1L1QCE - Compound Summary". PubChem Compound. USA: National Center for Biotechnology Information. 26 March 2005. Identification and Related Records. http://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?cid=8135. Retrieved 14 October 2011. 
2. ^ Buehler, C; Pearson, D.Survey of Organic Syntheses. Wiley-Intersciene, New York. 1970.
3. ^ Shriver, D; Atkins, P.Inorganic Chemistry. W. H. Freeman and Co., New York. 1999.
4. ^ Thomas Schiffer, Georg Oenbrink “Cyclododecatriene, Cyclooctadiene, and 4-Vinylcyclohexene” in Ullmann’s Encyclopedia of Industrial Chemistry, 2005, Wiley-VCH, Weinheim.
5. ^ John A. Soderquist and Alvin Negron (1998), "9-Borabicyclo[3.3.1]nonane Dimer", Org. Synth., http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv9p0095 ; Coll. Vol. 9: 95 
6. ^ Roger Bishop, "9-Thiabicyclo[3.3.1]nonane-2,6-dione", Org. Synth., http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=CV9P0692 ; Coll. Vol. 9: 692 Díaz, David Díaz; Converso, Antonella; Sharpless, K. Barry; Finn, M. G. (2006). "2,6-Dichloro-9-thiabicyclo[3.3.1]nonane: Multigram Display of Azide and Cyanide Components on a Versatile Scaffold". Molecules 11 (4): 212–218. doi:10.3390/11040212. http://www.mdpi.org/molecules/papers/11040212.pdf. 
7. ^ Schunn, R; Ittel, S. (1990). "Bis(1,5-Cyclooctadiene) Nickel(0)". Inorg. Synth.. Inorganic Syntheses 28: 94. doi:10.1002/9780470132593.ch25. ISBN 9780470132593. 
8. ^ Crascall, L; Spencer, J. (1990). "Olefin Complexes of Platinum". Inorg. Synth.. Inorganic Syntheses 28: 126. doi:10.1002/9780470132593.ch34. ISBN 9780470132593. 
9. ^ Irradiation of cis,cis-1,5-cyclooctadiene in the presence of copper(I) chloride George M. Whitesides, Gerald L. Goe, Arthur C. Cope J. Am. Chem. Soc., 1969, 91 (10), pp 2608–2616 doi:10.1021/ja01038a036
10. ^ Preparation and conformation of (E,E)-1,5-cyclooctadiene Dieter Boeckh, Rolf Huisgen, Heinrich Noeth J. Am. Chem. Soc., 1987, 109 (4), pp 1248–1249 doi:10.1021/ja00238a046
11. ^ (E,E)-1,5-Cyclooctadiene: a small and fast click-chemistry multitalent Henning Stöckmann, André A. Neves, Henry A. Day, Shaun Stairs, Kevin M. Brindle and Finian J. Leeper Chem. Commun., 2011 doi:10.1039/C1CC12161H